It signals a slight change in news consuming. The traditional way was that you have (at least one) a trusted source like times magazine, CNN, or “Der Spiegel” and “Tagesschau” in Germany which you read/see from start to end to get the information, which is important to you. Those “trusted sources” did the filtering for you, they decided what’s important and what not.
Today, some keen folks are part in social networks where they get kind of alerts like:

Which means that he marked this article as “worth reading” in a social network called digg. Since you are interested in the topic too you can start reading it without knowing the publishing source. Perhaps you have never read from that source before.
So the filtering of information in increasingly passed to your social network. What they read is important to you and vice versa.

In the result, traditional trusted sources in online media won’t be read from start to end. Users get a link to a story and leave the page after reading. so there are new ways required to keep the readers online and to become a part of social network information filtering.